After cleaving DNA Spo11 remains covalently attached to the 5' ends. Spo11 is removed by cleavage of the DNA and release of Spo11:oligonucleotide complexes (Neale et al. 2005, Pan and Keeney 2009). In yeast, the Mre11:Rad50:Xrs2 complex is required for processing of double-strand breaks introduced by Spo11 (Cherry et al. 2007). The homologous Mre11:Rad50:Nbs1 complex from mouse has not been observed to localize to double-strand breaks made by Spo11 on autosomes. The enzymes responsible for removal of Spo11 and resection of the 3' ends remain unknown.